1. Field of the Invention
The invention relates in general to spectrometric devices for efficient collection of light for analysis. More particularly, the invention relates to a light collecting mirror and optical fiber device for use in spectrum analysis.
2. Background of the Invention
In a light scattering experiment, scattered light is usually emitted in a 4xcfx80 solid angle and collected with an optical element such as a lens, mirror, or fiber. Only a fraction of the light is actually collected, however, because the solid angle intercepted by such an optical element is relatively small. Typical examples of such devices are shown in U.S. Pat. No. 5,680,209 entitled xe2x80x9cSpectroscopic systems for the analysis of small and very small quantities of substances.xe2x80x9d To increase the collection efficiency of light emanating from a sample, a light collecting device is needed that allows for optimal detection of the emitted light for spectrometric analysis. The present invention fulfills this need by providing a fiber optic/mirror device that is easy to use in both laboratory and field applications and provides for both the delivery of light to a sample and the optimal collection of light from the sample.
The invention relates to a device for efficient delivery of light to a sample and collection of most of the light scattered from the sample. The device comprises an ellipsoidal mirror, and several optical fiber legs that can be bundled together that illuminate the observed sample and collect light from the sample. The sample, residing either within a capillary tube or sample chamber, is placed at a first focal point of the ellipsoidal mirror along with a first leg of a light delivery and collection optical fiber. The light emitted in the solid angle facing this leg is collected by the fibers that comprise the leg. The remaining light is reflected by the inner surface of the ellipsoidal mirror, directed and focused at the second focal point of the ellipsoidal mirror, and provides additional light collection from the sample at a terminus of a second optical fiber leg positioned at the second focal point. Thus, most of the scattered light from the sample is collected by these two optical fiber collecting legs located at the focal points of the ellipsoidal mirror.
The mirror/optical fiber collection device can be used in either a laboratory or field application for very efficient light collection from a sample. Efficient light collection is critical, particularly in situations where very low light levels are observed or where scattering phenomena exists having a low cross section, such as in Raman scattering measurements. Accordingly, a system in accordance with the present invention provides a rugged and portable light collecting device using optical fibers for efficient delivery and collection of light for spectrometric applications. Moreover, a system in accordance with the present invention provides a device that is capable of more efficient radiation collection capability compared to presently used schemes of collecting light, and, at the same time is portable and inexpensive to produce and can be used in fluorescence, Raman, emission, and absorption spectral measurement based systems. Still further advantages will become apparent from consideration of the ensuing detailed description.